Enable ARM64 cryptographic extensions in iOS library builds

Go's internal/cpu never detects ARM64 features on GOOS=ios, so AES, AES-GCM
and SHA-256 use their generic implementations on iOS and tvOS. Patch the
Go source in the Apple library build to assert the ARMv8.0 cryptographic
extensions, as Go already does for macOS.

See https://github.com/SagerNet/sing-box/issues/4486

.github/workflows/build.yml

@@ -1246,6 +1246,9 @@ jobs:
         with:
           go-version: 1.26.7
           cache: false
+      - name: Patch Go for iOS
+        if: matrix.build && (matrix.platform == 'ios/arm64' || matrix.platform == 'tvos/arm64')
+        run: .github/patch_go_for_ios.sh
       - name: Cache Go modules
         if: matrix.build
         uses: actions/cache@v4
@@ -1265,6 +1268,8 @@ jobs:
         run: git tag v${{ needs.calculate_version.outputs.version }} -f
       - name: Build library
         if: matrix.build
+        env:
+          GOTOOLCHAIN: local
         run: |-
           make lib_install
           export PATH="$PATH:$(go env GOPATH)/bin"